Unwrap the Creme Eggs®, put in a freezerproof container and freeze for at least 2 hrs. You can do this up to two days in advance. It's important you don't skip this step, as it will ensure the Creme Eggs® don't explode during baking.

Beat the butter and all the sugars together using an electric whisk for 2-3 mins until well combined (or do this in a stand mixer). Add the vanilla extract and orange zest, then beat in the eggs, one at a time, beating well after each addition. Scrape down the bowl and mix again. Sift the flour and cocoa into the bowl, followed by the baking powder, bicarbonate of soda and sea salt, then beat until just combined. Stir in the chopped chocolate.

Line a baking tray with baking parchment. Roll the dough into eight equal-sized balls (about 90g each) using dampened hands. Arrange on the tray and chill for 1-2 hrs.

Remove the Creme Eggs® from the freezer. Working quickly, roughly flatten a dough ball in your hand, put a Creme Egg® in the middle and form the dough around it to enclose. Repeat with the remaining, then chill for 1 hr. At this stage, the dough balls will keep frozen for up to three months (see tip below).

Heat the oven to 200C/180C fan/gas 6. Line two large baking trays with baking parchment and arrange the cookies on it with at least 4cm between them. Bake for 10-11 mins until they have spread slightly but are still very thick. Cool on the tray for 15 mins, then serve slightly warm. Will keep for up to two days in an airtight container.